A compressor, such as a piston-reciprocation type multicylinder compressor for compressing refrigerant used in an automotive air conditioning system, often has such a configuration where a valve plate, on which a suction hole capable of communicating between a suction chamber and a cylinder bore and a discharge hole capable of communicating between a discharge chamber and a cylinder bore are formed, is interposed between a cylinder head having the suction chamber and the discharge chamber and a cylinder block having cylinder bores, and a discharge valve consisting of a reed valve for opening/closing the discharge hole is provided at the discharge hole of the valve plate, and the discharge hole is located at a tip side of the reed valve. The discharge hole is usually formed into a circle, and a reed valve constituting the discharge valve is formed into a shape blocking up the circular discharge hole. In such a compressor, particularly in a compressor where a discharge chamber is located at an outer side and a suction chamber is located at an inner side, a retainer-integrated gasket is generally used as a stopper regulating a lift of the discharge valve during opening the discharge valve.
However, because the amount of the lift of the discharge valve is regulated during discharge step, the area of the cross section of a flow path opened is kept comparatively small to generate the resistance of the flow path, so that accompanied over-compression might cause phenomena, such as (1) decrease of the refrigeration ability derived from the blow-by of refrigerant leaking to the side of the crank chamber or (2) increase of power consumption for driving the compressor, etc., so as to make the compressor efficiency worse.
As for such problems, Patent document 1 discloses a structure where a hole through which discharged gas can pass is formed on a valve spring which gives the discharge valve the elastic force in order to reduce flow loss of the discharged gas, however, its reduction effect of the flow resistance is not sufficient because the cross section cannot be increased so greatly.